These are things that must be taken in from the environment because your body cannot manufacture them and they promote specific chemical reactions in the body.

这些都是必须从外界摄取的物质,因为无法通过自身合成,它们能促进体内特定的化学反应

耶鲁公开课 - 关于食物的心理学、生物学和政治学课程节选

Because... you have to make these like, synthesized chemicals.

因为，你必须制作这些合成化学品。

对于古怪教授 - SpeakingMax英语口语达人

So if you're trying to make a more complicated organic molecule carbon-carbon bonds are one of the most difficult things to make in organic chemistry, and it turns out that c n minus is a very reactive molecule, so it's a good way, even though we'll go over some drawbacks in a second, it is a good way to make carbon-carbon bonds.

如果你要合成一个更复杂的有机分子,碳碳键是有机化学中,最难制造的键之一，而实际上氰离子是一种具有很高活性的分子，用它是一个好办法，尽管我们一会儿将看到它的一些缺点，但它的确是一个制造碳碳键的好方法。

麻省理工公开课 - 化学原理课程节选